Mobile communication devices, such as cellular telephones, communicate with other communication devices via one or more networks. Such networks may implement any of a variety of protocols, including Global System for Mobile Communication (GSM), Code Division Multiple Access (CDMA) and Wideband CDMA (W-CDMA). Often, the protocol may use a frequency band that overlaps with the frequency band of another protocol. For example, protocol A may operate on a frequency band of 1900-1950 MHz, while protocol B operates on a frequency band of 1945-2000 MHz. In this example, protocols A and B overlap between 1945 MHz and 1950 MHz.
Such overlap can cause operating errors on mobile devices. For example, a mobile device may be designed to communicate using only protocol A when using a frequency of 1947 MHz. However, the frequency 1947 MHz is a shared frequency because protocol B is also able to send and receive data on that frequency. Thus, if, while the mobile device is communicating using protocol A on 1947 MHz, data is sent on 1947 MHz using protocol B, the mobile device becomes “confused” and is unable to properly communicate using protocol A, as it was intended to do. If several frequencies are shared between multiple protocols, it may take an undesirably long time for a mobile device to locate a suitable frequency on which to transmit or receive data. If an excessive number of frequencies is shared between multiple protocols, a mobile device may become incapacitated, unable to send or receive signals on any frequency at all.